An unemployed 20-year-old went on an early morning shooting rampage in Orange County, Calif., today killing three people, and terrorizing several other motorists whom he shot at and carjacked, before taking his own life, police said.

After receiving dozens of 911 calls, and just as they were readying to confront him, police watched suspect Ali Syed jump from the last vehicle he stole that morning and almost instantaneously shoot himself in the head with a shotgun, authorities said.

Syed, 20, a part-time student at Saddleback College, began his hour-long killing spree just before 5 a.m. PT, in his parents' Ladera Ranch home, where he shot an unknown woman in her twenties, according to Tustin Police Chief Scott Jordan, who briefed reporters Tuesday afternoon.

Police have not yet identified the woman or determined her relationship to Syed.

His parents heard the shotgun blast and called police, while Syed fled with a shotgun in their black SUV, Tustin said.

Syed drove to a Denny's parking lot in nearby Tustin, Calif., where he confronted a driver waiting to carpool his son, and shot the motorist through the back window of his vehicle, the chief said. The unidentified man was wounded and remains in the hospital.

The suspect then stole a bystander's car from the Denny's lot and fled, according to Tustin Police Chief Scott Jordan, who briefed reporters Tuesday afternoon.

Syed is believed to have driven that car only briefly before pulling into a Mobile gas station and confronting another motorist.

From there he pulled the car over and began randomly shooting at drivers proceeding southbound on California Route 55, Jordan said.

He hit three cars, severely wounding one driver who was hit by either a bullet or shrapnel in the hand and face. That driver, who did not have a cell phone, managed to drive himself home and call police, Jordan said.

Syed then confronted another driver, stopped at a stopped sign.

"He approached the victim at gunpoint, walked him across the road and executed him, shooting him three times," the chief said.

That victim has not been identified.

Syed then pulled into the parking lot of Tustin computer store Micro Center, where he allegedly confronted his final victim, later identified as 26-year-old Jeremy Lewis.

Syed killed the man and stole his truck, according to police.

By then, "many calls were coming and [California Highway Patrol officers] got behind the stolen vehicle ... getting in position to make a felony car stop," Jordan said.

Before cops had the chance to confront him in the city of Orange, Calif., Syed "exited the vehicle while it was still in motion ... [and] almost instantly as he exited the vehicle, he took the shotgun, put it to his head and killed himself," the chief said.

Cops said they do not know Syed's motive. They said he acted alone and was not part of a larger conspiracy.